1. Field of the Invention
The invention relates to caterpillar track vehicle propulsion and more specifically to a heavy duty caterpillar track attachment to be adapted to a vehicle having a drive shaft and a steering mechanism.
2. Description of the Prior Art
Known in the art is U.S. Pat. No. 1,665,470 which describes a rear-end assembly for power driven vehicles, more specifically tractors. The rear-end assembly comprises a transmission mechanism adapted to receive the motive power from the differential of the vehicle, and to transmit it to a pair of rear drive wheels driving a pair of caterpillar tracks. It is assumed that the vehicle had been originally designed to undergo this transformation by having a special corresponding front assembly that is suitable to cooperate with the rear-end assembly. Therefore, if such a front assembly was not previously designed for that purpose, the rear-end assembly cannot be installed on the vehicle. The rear drive mechanism of the vehicle has to be mostly replaced by the rear-end assembly which comprises several moving or rotative parts that might as well be subjected to possible breakdown, reducing thereby the reliability of the assembly.
Also known in the art is U.S. Pat. No. 3,710,886 which describes a mechanism for converting a wheeled vehicle into a tracked vehicle. The mechanism comprises a pair of track assemblies adapted to be connected to the brake drums of the vehicle in replacement of the normal four wheels. The steering mechanism of the vehicle is further implemented through the brake system of the vehicle for controlling braking of the tracks to steer the vehicle. Such mechanism requires a complicated installation which leads to the track conversion. Furthermore, the whole weight of the vehicle is carried by adaptors joining the track assemblies to the wheels, therefore requiring very strong adaptors that will not be any way suitable for labor on soft or uneven grounds, especially for working the soil or the snow.
Also known in the art is U.S. Pat. No. 4,865,141 which describes a device for changing a vehicle provided with wheels into a track vehicle. The device resembles the one described in U.S. Pat. No. 3,710,886 above-mentioned. However, the two track aggregates are attached to the rims of the wheels of the vehicle instead of the brake drums, and this without the removal of the vehicle wheels. Although the construction of the aggregates also differs slightly from the prior one, the same drawbacks are observed.
Also known in the art are U.S. Pat. Nos. 1,810,138, 2,356,931, 3,976,153, 4,448,273 and 4,821,824 which all describe different kinds of caterpillar track devices providing track propulsion for a vehicle. However, all of these devices somehow or other require difficult installation, are intended for only some of the wheels of a vehicle and thus lacks stability on soft ground, and comprise various easily breakable structural parts that prevent such devices from being used for heavy work.
It is also worth mentioning that most of the prior art devices, when guiding the tracks from one extremity to the other, are provided with sets of idler wheels. Such idler wheels are in a way costly and do not necessarily represent the best means to perform this purpose.